<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
<p>
    请选择菜单：
    <select id="menu">
        <option value="chose">请选择</option>
        <option value="fruit">水果</option>
        <option value="cake">蛋糕</option>
        <option value="nuts">坚果</option>
    </select>
</p>
<p>该系列有：<span id="Variety"></span></p>
<script>
    // 此处写代码
    var meau = document.getElementById("menu");
    var Variety = document.getElementById("Variety");
    menu.onchange = function chose(){
        switch(this.value){
            case "chose" :
                break;
            case "fruit" :
                fruits();
                break;
            case "cake" :
                cakes();
                break;
            case "nuts" :
                nutss();
                break;
        }
    };

    function fruits(){
        Variety.innerHTML = "苹果,香蕉,鸭梨,橙子,西瓜";
    }
    function cakes(){
        Variety.innerHTML = "慕斯,海绵,戚风,奶油,提拉米苏";
    }

    function nutss(){
        Variety.innerHTML = "开心果,巴坦木,碧根果,腰果,呵呵";
    }
</script>
</body>
</html>
